FIG. 1 is a conventional illustration of a honeycomb body 102 prior to selected cells being sealed by a plugging material. The honeycomb body 102 is typically fabricated with a matrix of intersecting, thin, porous walls 104 surrounded by an outer wall 106, which in the illustrated example is provided a circular cross-sectional configuration. The walls 104 extend across and between a first end face 108 and a second end face 112. The matrix of intersecting, thin, porous walls 104 define corresponding channels 110 that define hollow passages extending between the first end face 108 and the second end face 112.
Conventional methods are known to seal one end of each of the channels 110 such that a first subset of channels are sealed at the first end face 108 and the second subset of channels are sealed at the second end face 112.
In operation, contaminated fluid (e.g., exhaust gas including particulate matter, such as exhaust soot) can be brought under pressure to an inlet face and enters the plugged honeycomb body 102 through one of the two subsets of channels that are open to an inlet face of the filter. Because this subset of channels is sealed at the opposite end face, i.e., the outlet face of the body, the contaminated fluid is forced through the thin porous walls 104 and into adjoining cell channels of the other of the two subset of channels that are open to the outlet face of the filter. As the fluid is forced through the porous walls 104, solid particulate entrained in the fluid can be filtered out such that a clean fluid stream eventually exits the outlet face of the filter.
FIG. 2 is a schematic view of a conventional apparatus 202 similar to the apparatus described in U.S. Patent Application Publication No. 2006/0131782, published Jun. 22, 2006. As shown, the apparatus includes a source 204 of pressurized plugging material. A valve 206 can be selectively opened to charge a plugging chamber 212 with a quantity of plugging material sufficient to carry out multiple plugging cycles.
FIG. 3 is a schematic view of a conventional skinning apparatus 250 including a conventional skinning control module 260. The skinning apparatus 250 is configured to supply skinning material from a source 252 of skinning material to apply the outer wall 106 to the periphery of the honeycomb body 102. The source 252 can include a skinning material reservoir 254 and a pump 256 configured to operate under the instruction of a controller 258. The skinning control module 260 includes a skinning piston 262 configured to reciprocate within a cylindrical portion 264 by a piston actuator 263. A conical extension 266 provides a fluid connection between the cylindrical portion 264 and a skinning material supply line 268. The skinning control module 260 also includes an upstream valve 270 and a downstream valve 272.
In operation, as shown in FIG. 4, the controller (i.e., 258 in FIG. 3) can open the upstream valve 270 and close the downstream valve 272. As shown in FIG. 5, the pump (i.e., 256 in FIG. 3) can then by activated to fill a skinning chamber 274 with skinning material from the source (i.e., 252 in FIG. 3) of skinning material. As shown in FIG. 6, the controller can then close the upstream valve 270 and open the downstream valve 272. As shown in FIG. 7, the piston actuator 263 can then extend the skinning piston 262 in direction 276 such that the skinning material is passed through the conical extension 266 and into the supply line 268. As shown in FIG. 7, the conical section houses residual skinning material outside of the supply line 268 even when the skinning piston 262 is in the fully extended position.
Turning back to FIG. 3, operation of the control module 260, as discussed with respect to FIGS. 4-7, does not directly regulate pressure of the skinning material 280 but allows control of the flow rate that skinning material 280 is dispensed by nozzle 278. At the desired dispensing flow rate, skinning material 280 may be adequately and efficiently applied to the surface of the honeycomb body 102 for subsequent smoothing by a doctor blade 282 as the honeycomb body 102 rotates about axis 284.